正则表达式用于在标点符号之前提取单词

Question

I'm trying to extract phrase which occur before a punctuation but is of the form capitalized words in a phrase.

Abstract Algebra . the area of modern mathematics that considers algebraic structures to be sets with operations defined on them, and extends algebraic concepts usually associated with the real number system to other more general systems, such as groups, rings, fields, modules and vector spaces.

Algebra. a branch of mathematics that uses symbols or letters to represent variables, values or numbers, which can then be used to express operations and relationships and to solve equations.

Algebraic Expression . a combination of numbers and letters equivalent to a phrase in language, eg x2 + 3x - 4.

Analytic (Cartesian) Geometry: the study of geometry using a coordinate system and the principles of algebra and analysis, thus defining geometrical shapes in a numerical way and extracting numerical information from that representation.

Inductive reasoning or logic: a type of reasoning that involves moving from a set of specific facts to a general conclusion, indicating some degree of support for the conclusion without actually ensuring its truth.

Currently I'm using the following regex:

(([? ])([A-Z][a-z\s]+)?([A-Z][a-z\s]+?[.:]))

I have two issues with this.

1. I think this is not the optimum way of writing it.
2. Its not capturing the ones where there are more than two words in a phrase

Answer 1

Try ^[AZ][^.,:';]+

Explanation:

^ - beginning of a line

[AZ] - single uppercase character

[^.,:';]+ - one or more of characters different from .,:';

Demo

Answer 2

One reason not matching more than 1 word for the current data is that the pattern starts with [? ] [? ] which will match either a space or question mark.

You might also omit some of the capturing groups and use a single one. Note that you don't have to make this match [az\\s]+?[.:] non greedy using a ? because the character class does not contain a . or :

To get the capitalized words followed by either . or : you could use:

\b([A-Z][a-z]+(?:\s+[A-Z][a-z]+)*)[.:]

Explanation

• \\b Word boundary
• ( Capture group 1
  • [AZ][az]+
  • (?:\\s+[AZ][az]+)* Repeat 0+ times matching AZ and 1+ times az
• ) Close group
• [.:] Match either . or :

Regex demo

If you also want to match words surrounded by ( and ) you might use an alternation.

\b((?:\([A-Z][a-z]+\)|[A-Z][a-z]+)(?:\s+(?:\([A-Z][a-z]+\)|[A-Z][a-z]+))*)[.:]

Regex demo